1. Field of the Invention
The present invention relates to apparatus and methods for protecting wildlife, and in particular, to applying such protection to outboard motors.
2. Description of Related Art
Outboard motors typically have an above-water engine coupled to an underwater propeller through a drive train contained inside a housing. The housing usually has extending on either side a horizontal flange acting as an anti-ventilation plate (also sometimes referred to as an anti-cavitation plate, or simply a cavitation plate). This plate is designed to prevent air from above the plate being sucked into the propeller, which would reduce its efficiency or, in extreme cases, prevent forward propulsion.
Outboard motors will also typically have a vertical keel (also referred to as a fin or skeg). This keel will tend to bias the propeller into alignment with the water flowing past the watercraft and thereby decrease destabilizing forces that might turn the propeller away from a neutral position.
Seaweed and fishing lines represent a serious problem for the propellers of watercraft, including the propellers of outboard motors. Entanglement with the propeller can impede and possibly damage the propeller, as well as its drive train and motor. Even if no damage occurs, this entanglement can cause significant drag that will slow the watercraft and reduce its range of operation.
Marine craft can pose a serious danger to aquatic wildlife. For example, manatees are often injured by the propellers of watercraft. The manatee is particularly susceptible since it spends a good portion of its day grazing in shallow waters. Even if the manatee avoids the propeller blades, the keel or skeg projecting below the propeller can by itself inflict serious injury.
Propeller and keel lacerations inflicted on a manatee can lead to infection, internal injuries, limited mobility and eventually death. A large percentage of the surviving manatee population is scarred from their encounters with the propellers and keels of outboard motors.
See also U.S. Pat. Nos. 2,136,628; 2,140,099; 2,723,641; 2,916,010; 4,057,028; 5,066,254; 5,176,550; 5,501,622; and 5,759,075.